from african-killer honest he bees in the southwest to louisiana to the spread of the burmese python in the florida everglades. all part of a scary trend. >> everywhere we look, we see species that are spreading and damaging our natural eco-systems now. and when scientists look into the future, they see the potential for many more damaging species. >> reporter: you make it sound like we're under attack everywhere. >> we are under attack everywhere. >> reporter: david lodge is a biologist at the university of notre dame. he says our agricultural system depends on plant and animal species imported to america, like wheat and cows and pigs. but that doesn't make them invaders >> an invasive species is a species that's been transported from one part of the planet to the other by people. and a species that has a harmful impact. >> reporter: and typically transported by design, by accident, a little bit of both? >> both. lots of invasive species have been transported by accident in the ball after water of ships or as a hidden pest on plants that have been imported. but many have also been i